1. Field
The field of the invention is fertilization of nutrient deficient trees and treatment of diseased trees, respectively.
2. State of the Art
Obtaining optimum food production from soil and other plant growing mediums is largely a problem of providing proper nutrition for production of increased biomass of the plants. Although green plants, being true autotrophs, supply the many organic components necessary for growth through photosynthesis, oxygen, carbon, hydrogen, and 13 known minerals are nevertheless required for lifetime development. However, nutrients present in the soil are not available to the plant unless in suitable chemical form, and various related soil and nutrient factors are also involved. Paramount among these are the concentrations of the nutrient in the soil, the solubility of the nutrient when present, its cation charge capacity, the root form and structure of the plant being grown, the texture and structure of the soil, the atmosphere, and the acidity or alkalinity of the soil.
Natural soils vary with respect to these growth influencing factors. For example, the productivity of desert and short grass prairie soils in the western United States is only one or two percent the productivity of wet lands in Georgia. Although this is partially the result of low rainfall in the west, poor soil fertility and structure are also involved.
The addition of missing nutrients to the soils has been long practiced with beneficial results. However, current practices, generally the simple addition of fertilizers to soils, may be very wasteful, unnecessarily expensive, inefficient in terms of plant utilization, and even detrimental to the environment. A significant amount of fertilizer is lost directly through leaching and is not available when needed during the growing period. Sometimes the nutrient becomes captured in insoluble compounds and is unavailable for plant utilization. Essential nitrogen fixing bacteria and mycorrhizai fungi may be lacking, which are very important to root growth for healthy plant growth. Another common problem is application of excess quantities of nutrient salts, resulting in plant "burn", with stunted growth or even death of the plant.
These problems have caused consideration of more sophisticated methods of providing nutrient treatment agents to the deficiently nourished plants. One approach is to bypass the soil solubility problem and to instead supply iron directly to the above ground parts of the plants such as the direct foliar application of the nutrients. Foliar sprays of iron compounds have been demonstrated to increase greening of leaf and stem tissues. A problem with this procedure is the limited penetration of the iron from the leaf surface into the chloroplast. The inclusion of a wetting agent and/or a carrying compound in the spray increases surface dispersion of spray droplets to enhance absorption. Such inclusion minimizes the "green island spotting" commonly observed with foliar iron application. This procedure requires repeated application throughout the season, since both new and existing growth require nutritive aid.
In addition to soil application and foliar spray application of iron compounds, lime-induced chlorosis in trees has for many decades been treated by introduction of iron compounds directly into the trunks of trees so effected. One method involves implantation of solid iron salts or of liquid injector devices into shallow holes bored into the trunk of the chlorotic tree. A number of forms of iron have been used, among them ferrous sulfate and ferrous citrate. The iron passes into solution in the tree trunk and moves to the foliage by way of the transpirational stream of the tree. In oak and white pine trees, application has noted beneficial effects of such treatment, but phytotoxicity and necrosis at the site of injection has been reported in susceptible species like citrus trees. It is often difficult to control the dissolution rate and concentration of iron going into the tissue of the tree trunk, which results often in tissue damage.
Prior investigators have implanted capsules which include various treatment agents into the tree trunk to correct mineral deficiencies and diseases in trees. (U.S. Pat. Nos. 3,706,161; 3,912,752; and 3,304,655).
One such implant which is shown in prior art FIG. 6 comprises a cartridge 1 having a hollow body 2 in which a capsule (not shown) of cellulose or gelatin containing the treatment agent is disposed. A plurality of slits 3 allow the treatment agent in the capsule to migrate into the tree trunk upon insertion into a hole bored into the tree trunk. A plurality of spring-locking tabs 4 retain the cartridge within the hole in the tree trunk and a cap 5 of sealing wax seals the hole. Such gelatin capsules are not water soluble under normal temperature and conditions, although they are soluble in hot water (Budavari, S., 1989. The Merck Index, p. 685) and as such restrict the passage of treatment agent into the tree. No practical method of implanting capsules so as to attain needed concentrations of nutrients, fungicides or other treatment agents to control diseases has been achieved. Such cartridges containing a cellulose or gelatin capsule release the treatment agent at irregular rates and leave the non-degradable plastic cartridge inside the tree trunk tissue and residues of the treatment agent remain in the gelatin capsule. Also, gelatin capsules are insoluble in water at temperature below 35-40.degree. C. and are insoluble in organic solvents (Budavari, S., 1989. The Merck Index, pp 685). The sap in the tree trunk tissue does not use up all the treatment agent before the injection hole is sealed off by callus tissue. Only water soluble chemicals can be used in this method to treat the tree. This is a limitation for pesticides since most are of limited solubility (e.g. dimetholate) or insoluble in water. As will be explained subsequently, the main component used in the present invention is widely used in the chemical industry as a solvent for many chemicals that are insoluble in water, which makes it advantageous over these prior art methods.
Another method of introducing treatment agents into a tree trunk is direct injection such as by means of a plastic injection syringe 6, (Prior Art FIG. 7) which contains a liquid (not shown) containing a treatment agent for injection into the tree trunk through an attached tube 8 when a piston 9 is depressed and locked. Such injection syringes 6 contain only small amounts of fluid and must be spaced every 5-6 inches around the trunk of the tree. Growers must remove the syringes after a few hours or a few days of treatment which is time consuming. Also, the cost of the injection syringes greatly exceeds that of the injection material. Direct injection of liquids is highly labor-consuming, since the injectors must be removed after a few hours or the next day after they are empty. Where a liquid pesticide is used, the injectors require special handling, and need to be disposed of in an environmentally safe place. Accordingly, they cannot be used in residential areas because the injector is completely exposed, only the injector tube or nozzle being inserted into the tree, with the cylinder containing the liquid outside and exposed. However, such method has been found particularly effective in arid and semi-arid areas, especially where the soils are calcareous wherein a growing tree is unable to utilize the iron in the soil. The direct injection of iron compounds into the trunk of the tree often effectively corrects the iron deficiency for a full growing season.
Another method of introducing a treatment agent into a tree trunk has been reported by North (1962) pp. 138-142 and Wallace and Wallace (1986) pp. 981-986. A hole is bored into the tree trunk and a reservoir of liquid including a treatment agent is attached. The treatment agent flows into the tissue and is translocated within the tree. This method is likely to produce an extensive necrotic area. Liters of liquid may be required, and concentrated liquids may be translocated too rapidly causing toxicity because of immediate excess availability of the liquid. Phytotoxicity is a major problem especially if concentrated nutrient solution is used. Phytotoxicity resulted after 24 to 48 hours of treatment of citrus trees injected with 1, 3 and 5 ml of each of 5% Fe and 8% Fe. Even with diluted solutions of 1 ml of 5% Fe with 4 ml of water and with 10 ml of water resulted in phytotoxicity in a navel orange tree after 48 hours. After about 12 hours of the treatment, the leaves of the treated plants started to fold upward and after a few days turned yellow-brown in color. The phytotoxicity is mainly due to the rapid absorption of the nutrient to the leaves in concentrations far in excess in the amount needed by the plant.
A need therefore remains for an effective, economical means of providing nutrients and pesticides, both water soluble and insoluble, at controlled rates to above-ground portions of trees without harmful side effects.